This invention relates to ice makers and, more particularly to means and method for indicating when water in an ice maker mold is frozen.
Ice makers and methods adapted to cyclically undergo a series of operations, including the filling of a mold with water to be frozen, the freezing of water in the mold to produce ice pieces, and the removal of the ice pieces from the mold have been well known in the art. It is common to have such ice makers in household refrigerators having a below-freezing compartment in which the ice maker is installed. Various ice makers and methods have been utilized to sense the completion of the water freezing operation of an ice maker and thereupon initiate an ice removal operation of the ice maker. For instance, there has been one practice to initiate the ice removal operation in an automatic ice maker by means of apparatus intended to sense the temperature of the contents of the ice mold; i.e., thermostats or the like have been employed to measure the temperature of the contents of the ice mold, or of some portion of the mold adjacent the contents, and terminate the ice freezing operation and initiate an ice removal operation when a temperature is sensed which is low enough to indicate that the entire contents of the mold are in a frozen state. This arrangement is quite reliable on ice making apparatus having a stationary ice mold with a mechanical pusher which actually displaces the ice pieces from the mold. This type of ice maker is shown and described in U.S. Pat. No. 3,654,772. However, in ice makers that incoporate a flexible ice mold which is twisted to loosen the cubes which then fall from the overturned tray, it sometimes occurs that the ice pieces near the temperature sensor do not fall from the mold, but remain in place for the next cycle, whereupon the sensor will give a false signal. A flexible ice mold type of ice maker is shown and described in U.S. Pat. Nos. 3,252,293 and 4,142,377. In many of the flexible ice mold ice makers, a temperature sensor is not used, but rather a clock or timer is used which integrates compressor run time and at some predetermined time period, the clock will signal when the ice piece removal operation is to be initiated. This type of ice maker is shown and described in U.S. Pat. No. 3,623,336. The use of a timer, however, has the disadvantage that in order to make certain that all ice pieces are frozen, the predetermined time period must be much longer than is normally required for complete freezing, resulting in a daily ice rate which is lower than necessary .
Ice makers can also be controlled as to the time to initiate the ice removal operation, not by the temperature of the ice mold or its contents, but rather by the temperature of a thermal system analogous to the ice mold and its contents. The thermal system would include a heat storage body or mass thermally disassociated from the ice mold and its contents but subjected to the same refrigerating effect as is the ice mold in such a manner that the rate at which heat is removed from the heat storage mass should be analogous to the rate at which heat is removed from the contents of the ice mold. This type of an ice maker control system is shown and described in U.S. Pat. No. 2,941,378. Such an ice maker control system does not, however, take into account the fact that incoming water to refill the ice mold is relatively warm and its temperature can vary considerably from one time to another and from one geographical location to another. For instance, incoming water in the summer is much warmer in most cases than it is in the winter. Incoming water for an ice maker located in warm geographical regions is warmer generally than it is in cold regions. The thermally disassociated heat storage mass does not compensate for the temperature difference between it and the incoming warm water in the ice mold.
By my invention there is provided an ice maker and method which will provide a signal to initiate an ice removal operation when the water is frozen in the ice mold. The ice maker and method eliminates the problems noted above with regard to prior ice makers and controls therefor.